1. Field of the Invention
This invention relates to fibre webs and has particular reference to the production of continuous filament cellulosic fibre tow webs. In GB-A-1387566 there is described a process for improving the properties of a continuous filament tow web by suspending a running tow in a flowing liquid in the form of a spread band, overfeeding the spread tow onto a moving foraminous support separated from the liquid and to form a coherent web, drying the web and then stretching the web to pull it back into tow form.
2. Description of Related Art
It has now been discovered that by adopting a modification to the process described in GB-A-1387566, the contents of which are incorporated herein by way of reference, an improved tow web structure can be produced.
The present invention is concerned with the production of a continuous tow web of viscose cellulosic fibres. As is well known, viscose cellulosic fibres are produced by spinning viscose dope in the form of a solution of sodium cellulose xanthate having a cellulose content in the range 5 to 12% by weight and a caustic soda content of 4 to 10% preferably 5 to 7% by weight into an acidic regeneration bath, typically containing 7 to 10% sulphuric acid, 10 to 28% sodium sulphate, and 0 to 4%, more specifically 0.5 to 1.5%, zinc sulphate in a bath at 30.degree. to 70.degree. C., more specifically 45.degree. to 60.degree. C., so as to neutralise the alkali and to coagulate and regenerate the cellulose to form cellulosic fibres. The viscose dope may have a full range of salt figures, although 4 to 12 are preferred. Regeneration occurs from the surface of the fibres, where a skin of cellulose is initially formed, through into the interior of the fibres.